In　this　work,　pristine　Li-rich　layered　Li1.2Ni0.2Mn0.6O2　(LNMO)　oxide　microspheres　are　synthesized　by　a　co-precipitation　method,　and　amorphous　SiO2　is　used　to　modify　the　LNMO　material　via　a　sol-gel　method.　The　structures　and　morphologies　of　both　the　pristine　and　SiO2　coated　materials　are　investigated　by　X-ray　diffraction　(XRD),　scanning　electron　microscopy　(SEM),　and　transmission　electron　microscopy　(TEM).　The　result　of　SEM-EDS　and　TEM　demonstrate　that　the　SiO2　was　successfully　coated　on　the　surface　of　the　LNMO　microspheres.　The　sample　modified　with　optimized　amount　(0.5　wt　%)　of　SiO2　presents　obviously　improved　initial　coulombic　efficiency,　cyclic　capacity,　high　rate　performance.　It　can　deliver　high　discharge　capacity　of　100.0　mA　h　g(-1)　at　10C　after　50　cycles　at　1C　which　is　much　higher　than　the　pristine　material.　By　the　comparison　of　cyclic　performance　in　electrolytes　containing　with　1000　and　2000　ppm　water　respectively,　SiO2　coating　layer　shows　a　superior　absorption　of　hydrofluoric　acid　(HF).　The　SiO2　coated　samples　also　present　superior　thermal　stability　proved　by　cycling　at　1　C　and　60　degrees　C.　The　analysis　of　electrochemical　impedance　spectroscopy　(EIS)　demonstrate　that　the　SiO2　coating　layer　can　protect　the　Li-rich　cathodes　by　decreasing　the　side　reactions　of　LNMO　with　the　electrolyte,　increasing　lithium　ion　diffusion　coefficients　and　lower　the　charge　transfer　resistance.　(C)　2017　Elsevier　B.V.　All　rights　reserved.